1. Field of the Invention
The present invention relates to a rotary sensor, and more particularly to a rotary sensor capable of accurately detecting an angle of rotation to be transmitted from the outside.
2. Description of the Related Art
With reference to the drawings, the description will be made of a conventional rotary sensor. FIG. 18 is an essential sectional view showing a conventional rotary sensor under application by Japanese Patent Laid-Open Application No. 2000-88510 and U.S. patent application Ser. No. 09/390463 corresponding thereto.
As shown in FIG. 18, the conventional rotary sensor has a casing 30 being, for example, box-shaped (not shown) in external shape, made of synthetic resin material or the like, and this casing 30 has a base portion covered with a bottom wall 31. Part of the bottom wall 31 is caused to project on the right side in the figure to thereby form a substantially cylindrical storage portion 32, and this storage portion 32 is formed by a surrounding side wall 33 and a base plate 34 at the base portion.
At the substantially central portion of the base plate 34, there is formed a supporting portion 34a for projecting in the left direction in the figure on the storage portion 32 side, and at the center of this supporting portion 34a, there is formed a semi-spherical bearing portion 34b including a recess.
Near a side wall 33 within the storage portion 32 on the base plate 34, there is projectingly formed a substrate holding portion 34c for mounting a resistor substrate 37 to be described later.
Within the storage portion 32, a substantially disk-shaped rotor 35 made of synthetic resin material is rotatably housed. This rotor 35 has an engaging portion 35a and a shaft portion 35b which are projectingly formed on one side above the rotor 35 as shown and on the other side below at a center of rotation with a center line A as the center of rotation respectively in such a manner that this shaft portion 35b is supported by a supporting portion 34a formed at the base plate 34.
The engaging portion 35a has two engaging walls 35c and 35c which are projectingly formed with the center line A being interposed therebetween, and between these two engaging walls 35c and 35c, there is formed a groove portion 35d having a predetermined width extending in a direction perpendicular to the center line A.
The respective tip end portions of the engaging walls 35c and 35c have substantially semi-circular protruded portions 35e and 35e formed projectingly on the groove portion 35d side respectively.
Also, the shaft portion 35b of the rotor 35 has a tip end portion projectingly formed in a substantially semi-spherical shape, and this shaft portion 35b is rotatably supported by a bearing portion 34b of the base plate 34, and is adapted not to move in a direction perpendicular to the center line A.
On the side of the rotor 35 on the side on which the shaft portion 35b has been formed, there is mounted a moving contact piece 36a with a spring operation, which is a part of a component constituting an angle detecting member 36.
This moving contact piece 36a is formed with a contact portion (not shown) which slides in contact with a resistor pattern and a collector pattern (not shown) to be described later.
On the opposite side to a surface to which the moving contact piece 36a is mounted, there is disposed a resistor substrate 37 with a predetermined clearance spaced, and this resistor substrate 37 is positioned at a substrate holding portion 34c of the base plate 34 to be fixed by means of caulking or the like.
The surface of the resistor substrate 37 is formed with the resistor pattern and the collector pattern (not shown) by means of printing or the like, and the moving contact piece 36a is adapted to come into elastic contact with the resistor pattern and the collector pattern (not shown).
Also, the resistor substrate 37 is formed with a through-hole 37a at its substantially central portion, and in this through-hole 37a, the supporting portion 34a of the base plate 34 is inserted, and the tip end of the supporting portion 34a is projectingly disposed on the side of a surface on which the resistor pattern and the collector pattern (not shown) are provided.
In this respect, the angle detecting member 36 is constituted by the moving contact piece 36a, and the resistor substrate 37 having the resistor pattern and the collector pattern (not shown).
Below the resistor substrate 37, a plurality of substantially L-character-shaped terminals 38 are connected correspondingly to the resistor pattern and the collector pattern (not shown), and this terminal 38 is drawn out of the end surface of the resistor substrate 37, and is connected to the tip end portion 38a drawn out on the left side in a state abutted against the inner surface of the side wall 33, to a lead pattern (not shown) on a FPC39 by means of soldering or the like.
Above the rotor 35, there is disposed an upper plate 40 for closing the storage portion 32 as a cover, and this upper plate 40 is mounted to mounting protrusions 31a formed at plural places on the bottom wall 31 and is fixed thereto by means of thermal caulking or the like.
At the central portion of the upper plate 40, there is formed an aperture 40a in which the engaging portion 35a of the rotor 35 is located, and around this aperture 40a, there is formed a supporting wall 40b, which is projectingly formed in a cylindrical shape on the internal rotor 35 side. Thus, the rotor 35 is adapted not to incline more than a predetermined value by means of the supporting wall 40b. 
Between the upper plate 40 and the rotor 35, there is formed a clearance portion 41, and in this clearance portion 41, there is disposed an elastic member 42. This elastic member 42 is made of plate material annular in external shape with a spring operation such as a phosphor bronze plate, and flat mounting portions (not shown) are formed at plural places constituting a ring shape.
Also, in the elastic member 42, by curving a part of its annular portion in a wave-shape, elastically-contacted portions (not shown) are formed at plural places, and this elastic member 42 is caulked to a protrusion (not shown) formed on the rotor 35 side. The spring pressure of the elastic member 42 is set to be greater than that of the moving contact piece 36a. 
Thus, the elastically-contacted portions (not shown) always come into elastic contact with the rotor 35 at plural places of the elastic member 42, whereby the rotor 35 is pressed against the base plate 34 side, the shaft portion 35b is supported by the bearing portion 34b of the supporting portion 34a, and rotation of a driving shaft 43 to be described later is transmitted so that the rotor 35 is rotatably supported within the storage portion 32.
Also, the rotor 35 is supported with the supporting portion 34a as a fulcrum in such a manner that the engaging portion 35a can move obliquely and return in any direction perpendicular to the center line A, which is the center of rotation, by the operation of the elastic member 42.
In order to detect an angle of rotation of a throttle valve for, for example, an automobile or the like through the use of a rotary sensor having the above-described structure, the casing 30 is first mounted to the main body of a throttle body (not shown). Then, as shown in FIG. 18, a driving shaft 43 coupled to the rotating shaft (not shown) or the like of the throttle valve is inserted into the groove portion 35d of the engaging portion 35a of the rotor 35 for being positioned.
This driving shaft 43 is formed in a circular rod shape, and at its tip end portion, there is formed a flat plate-shaped protruded portion 43a passing through the center line A, which is the center of rotation. The driving shaft 43 is adapted to reciprocatively rotate within a predetermined range of angle of rotation.
Thus, the protruded portion 43a is inserted into the groove portion 35d of the rotor 35, and the driving shaft 43 engages the engaging portion 35a so that the rotor 35 rotates following the rotation of the driving shaft 43. In this respect, when the protruded portion 43a is inserted into the groove portion 35d in an off-center state at that time, the rotor 35 obliquely moves to thereby couple the two.
In the conventional rotary sensor, however, the supporting portion 34a of the base plate 34 is inserted through the through-hole 37a of the resistor substrate 37, and the tip end of the supporting portion 34a is projectingly disposed on the side of the surface, on which the resistor pattern and the collector pattern (not shown) have been provided. In this state, the shaft portion 35b of the rotor 35, which has been projectingly formed in a substantially semi-spherical shape, is rotatably supported by the bearing portion 34b provided at the supporting portion 34a. In this state, the rotation of the rotor 35 causes the shaft portion 35b and the bearing portion 34b to chafe against each other.
This chafing may generate shavings. Since the bearing portion 34b is a recess and does not move, but is further coated with grease, the shavings temporarily accumulate in a small clearance between the bearing portion 34b and the shaft portion 35b or its periphery, and further are kneaded with grease to become comparatively large.
Thus, when the rotation of the rotor 35 is stopped and it is rotated again, these temporarily accumulated shavings or comparatively large shavings may adhere onto the side of the surface of the resistor substrate 37, on which the resistor pattern and the collector pattern (not shown) have been provided.
When these temporarily accumulated shavings or comparatively large shavings adhere onto the side of the surface of the resistor substrate 37 and the collector pattern as described above, there arises a problem that the electric characteristics and service life of the rotary sensor will be adversely affected.
A rotary sensor according to the present invention solves the above-described problems, and its object is to provide a rotary sensor having a long service life, capable of maintaining the stable electric characteristics.
A rotary sensor according to the present invention comprises: a rotor having an engaging portion, with which the driving shaft engages; a casing for rotatably supporting the rotor; and an angle detecting member housed within this casing, for being operated by the rotation of the rotor, wherein
the rotor has an engaging portion located forward; and a shaft portion located at the rear on the opposite side, provided at the rotor-central portion of the rotor, the casing has a supporting portion provided at a position opposite to the shaft portion of the rotor, there is formed a recess at the shaft portion of the rotor, there is formed a convex-shaped conical portion in the supporting portion of the casing, and there is disposed a conical portion within the recess, and the shaft portion is supported by the conical portion fitted in the recess.
In the rotary sensor according to the present invention, the angle detecting member has a resistor pattern or an electric conductor pattern constituting a portion thereof, and the resistor pattern or the electric conductor pattern is provided on one surface on a flat plate-shaped proximal portion having a through-hole, and the tip end portion of the shaft portion is inserted through the through-hole beyond one surface of the proximal portion.
Also, in the rotary sensor according to the present invention, the casing has a bottom wall provided with the supporting portion, and between the bottom wall and the proximal portion, there is provided a clearance portion.
Also, in the rotary sensor according to the present invention, the supporting portion is formed of metallic material separated from the casing, and the supporting portion is held by the casing.
Also, in the rotary sensor according to the present invention, at the tip end of the shaft portion, there is provided a cylindrical portion, the recess is constituted by a circular hole located at the cylindrical portion and a conical recess formed within this circular hole, the protruded portion has a conical portion provided on the tip end side and a circular column portion on the base side, contiguously provided to the conical portion and the circular column portion is fitted into the cylindrical portion in such a manner that the cylindrical portion is guided by the outer peripheral surface of the circular column portion and the rotor is pivotally supported by the supporting portion.